Perhaps I’m “talking to” some reputable member of the community who has made a post with an explanation, and I’m using his words as an argument in a related discussion, but not the one it’s been posted in.
You have a popular blog (and are quite fond of quoting it in arguments) - would you really consider everybody doing so “talking to you directly”?
Besides, I’m fine with the referenced user getting a notification of being quoted - but that’s a different concept than a reply.
Except maybe I’d want everything that comes with a structured expandable quote (link to post, unrolling, etc.).
So your idea of discussion is that everybody replies directly to the topic, and doesn’t engage in topical discussion with any other commenter? That’s a comment system, not a discussion system.
For example, let’s say the topic is “Opinions on Discourse”. I voice an opinion, someone disagrees with me, I disagree with them, and what then? Do we split off a “Opinions on Discourse - an argument between @Maciejasjmj and @someuser” thread? Should everybody do that whenever they engage in a conversation with another commenter? Or do we lock up the whole thread for other users?